Ron Bowes, the man who collected and published personal details from 100
million Facebook users, has said he did so to learn how to break passwords.

Mr Bowes said he harvested the information, which was publicly available from users with low privacy settings, in order to help him work on a piece of security software.

The list, which was published on a filesharing service called BitTorrent, contains the user's profile, name and unique ID.

Mr Bowes, a Canadian security consultant, told BBC News that his current work for Nmap Security Scanner involved testing password policies of organisations using what he calls "brute force attacks" - guessing every username and password combination.

By collecting names used on Facebook, he said he could hone and improve his password hacking software.

He said that by knowing a user's first name and surname it was possible to test a number of password combinations as part of his work on a software tool called Ncrack.

Researchers could then combine this list with a catalogue of the most commonly used passwords to test the security of websites. However, a similar technique could be used by cybercriminals to crack computer software.

Although all the data harvested was publicly available if anyone since changed their Facebook privacy settings, their information would still be accessible via this list.

Simon Davies from the watchdog Privacy International said that since more personal information had not been included in the trawl this was more of an "ethical attack" on user's personal details, meaning that individuals are unlikely to have been put at risk.

"This is a reputational and business issue for Facebook, for now," he said

Mr Bowes file has spread rapidly across the net.

On Pirate Bay, the world's biggest filesharing website, the list was being distributed and downloaded by thousands of users.

Facebook confirmed that the information in the list was already freely available online.

"I am of the belief that, if I can do something then there are about 1,000 bad guys that can do it too," he said.

"For that reason, I believe in open disclosure of issues like this, especially when there's minimal potential for anybody to get hurt.

"Since this is already public information, I see very little harm in disclosing it."

Earlier this year Facebook users complained over the complexity involved in navigating privacy settings. Following changes to simplify the process people still have to opt out of the default setting which automatically makes a certain amount of information publicly available by a search engine.